﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
using System.Text;

namespace Se.Net.Http
{
    public class HttpWebResponseUtility
    {
        private static readonly string DefaultUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

        /// <summary>
        /// 创建GET方式的HTTP请求
        /// </summary>
        /// <param name="url">请求的URL</param>
        /// <param name="timeout">请求的超时时间</param>
        /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
        /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>
        /// <param name="parameters">Querystring 参数</param>
        /// <returns></returns>
        public static HttpWebResponse CreateGetHttpResponse(string url, int? timeout, string userAgent, Encoding requestEncoding, CookieCollection cookies, IDictionary<string, string> parameters, Dictionary<string, string> queryString)
        {
            var request = CreateHttpRequest(url, timeout, "GET", userAgent, requestEncoding, parameters, queryString, cookies);
            return request.GetResponse() as HttpWebResponse;
        }
        /// <summary>
        /// 创建POST方式的HTTP请求
        /// </summary>
        /// <param name="url">请求的URL</param>
        /// <param name="parameters">随同请求POST的参数名称及参数值字典</param>
        /// <param name="timeout">请求的超时时间</param>
        /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
        /// <param name="requestEncoding">发送HTTP请求时所用的编码</param>
        /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>
        /// <returns></returns>
        public static HttpWebResponse CreatePostHttpResponse(string url, int? timeout, string userAgent, Encoding requestEncoding, CookieCollection cookies, IDictionary<string, string> parameters, Dictionary<string, string> queryString)
        {
            var request = CreateHttpRequest(url, timeout, "POST", userAgent, requestEncoding, parameters, queryString, cookies);
            return request.GetResponse() as HttpWebResponse;
        }

        /// <summary>
        /// 发送httpResponse
        /// </summary>
        /// <param name="url"></param>
        /// <param name="timeout"></param>
        /// <param name="method"></param>
        /// <param name="userAgent"></param>
        /// <param name="requestEncoding"></param>
        /// <param name="cookies"></param>
        /// <param name="parameters"></param>
        /// <param name="queryString"></param>
        public static void SendHttpRequest(string url, int? timeout, string method, string userAgent, Encoding requestEncoding, CookieCollection cookies, IDictionary<string, string> parameters, Dictionary<string, string> queryString, Action<IAsyncResult> respCallback)
        {
            var request = CreateHttpRequest(url, timeout, method, userAgent, requestEncoding, parameters, queryString, cookies);

            request.BeginGetResponse(new AsyncCallback(respCallback), null);
        }

        private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
        {
            return true; //总是接受
        }

        /// <summary>
        /// 转换为url中的querystring字符串
        /// </summary>
        /// <param name="parameters"></param>
        /// <returns></returns>
        private static string GetQueryString(IDictionary<string, string> parameters)
        {
            StringBuilder sb = new StringBuilder();
            if (parameters == null || parameters.Count <= 0)
                return sb.ToString();

            foreach (var param in parameters)
            {
                sb.Append(param.Key).Append("=").Append(param.Value).Append("&");
            }

            return sb.ToString().TrimEnd('&');
        }

        /// <summary>
        /// 创建Http请求
        /// </summary>
        /// <param name="url">请求的URL</param>
        /// <param name="timeout">请求的超时时间</param>
        /// <param name="method">POST GET</param>
        /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
        /// <param name="requestEncoding">发送HTTP请求时所用的编码</param>
        /// <param name="parameters">请求参数</param>
        /// <param name="queryString">QueryString</param>
        /// <param name="cookies"></param>
        /// <returns></returns>
        private static HttpWebRequest CreateHttpRequest(string url, int? timeout, string method, string userAgent, Encoding requestEncoding, IDictionary<string, string> parameters, IDictionary<string, string> queryString, CookieCollection cookies)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }
            if (queryString != null && queryString.Count > 0)
            {
                url += "?";
                url += GetQueryString(queryString);
            }
            HttpWebRequest request = null;
            //如果是发送HTTPS请求
            if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
            {
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                request = WebRequest.Create(url) as HttpWebRequest;
                request.ProtocolVersion = HttpVersion.Version10;
            }
            else
            {
                request = WebRequest.Create(url) as HttpWebRequest;
            }

            request.Method = method;
            request.ContentType = "application/x-www-form-urlencoded";
            if (!string.IsNullOrEmpty(userAgent))
            {
                request.UserAgent = userAgent;
            }
            else
            {
                request.UserAgent = DefaultUserAgent;
            }

            if (timeout.HasValue)
            {
                request.Timeout = timeout.Value;
            }
            if (cookies != null)
            {
                request.CookieContainer = new CookieContainer();
                request.CookieContainer.Add(cookies);
            }

            if (parameters != null && parameters.Count > 0)
            {
                StringBuilder sbBuffer = new StringBuilder();
                int i = 0;
                foreach (string key in parameters.Keys)
                {
                    if (i > 0)
                    {
                        sbBuffer.AppendFormat("&{0}={1}", key, parameters[key]);
                    }
                    else
                    {
                        sbBuffer.AppendFormat("{0}={1}", key, parameters[key]);
                    }
                    i++;
                }
                byte[] data = requestEncoding.GetBytes(sbBuffer.ToString());
                using (Stream stream = request.GetRequestStream())
                {
                    stream.Write(data, 0, data.Length);
                }
            }

            return request;
        }
    }
}
